The new home of the Nets, Brooklyn’s Barclays Center, played host to its first championship boxing card Saturday night.

Nets coach Avery Johnson thinks his team could learn a thing or two from those boxers that fought on the same arena floor where his team will take on the Knicks in the season opener in a little over a week.

“We don’t have a hit-first mentality,” Johnson said following yesterday’s open practice at the arena, “and if you don’t have a hit-first mentality you’re going to get hit. That’s what I’m talking about.

“It’s not about a turnover or a guy forgetting a play. No, I’m talking about defensively … we haven’t done a good job. I don’t care if we’re fatigued, I don’t care if we haven’t practiced, we haven’t done a good job of protecting the paint. For us to go where we want to go, we’ve got to be able to protect the paint a lot better than we have.”

Yesterday’s practice, by all accounts, was a spirited one, with Johnson half-joking there were two or three incidents that nearly escalated to the levels of Saturday’s fight card. But after spending more than a week without conducting a single practice because the Nets had to play five preseason games in seven days, it was just the kind of day the team needed.

“We had a good practice today,” said Deron Williams. “I think that’s where it starts. We had a couple tough games, I think, on both sides of the ball, and the way you correct those is watching film and then practicing. We had five in seven nights, so we haven’t had a chance to practice.

“Every practice we had coming into the preseason was great, and we were getting better, and we have a set of games but we still need practice. You get away from your principles, you get away from good habits you’re taught every day at practice, so now we get a chance to get back into those things.”

After spending the summer putting together a new roster almost entirely composed of players who have little, if any, experience playing together, it’s not unexpected it has taken some time for things to come together.

But regardless, Johnson made it clear he hasn’t been pleased with the way things have gone so far, particularly in the Nets’ back-to-back losses to the Celtics and Sixers last week.

“We haven’t had the type of defensive intensity [and] physicality that I’m looking for,” Johnson said. “This team does not have the personality I thought it would have at this point. That’s been somewhat of a disappointment.

“Are they trying? Yes. Is anybody panicking? No. But we should have a little more of a physicality and a presence and communication on a loud level on the court, and we haven’t gotten that consistently.”

* Backup guards C.J. Watson (hip pointer), Keith Bogans (bruised tailbone) and Jerry Stackhouse (sore right hamstring) sat out of practice, while Andray Blatche and Josh Childress both suffered minor left ankle sprains during practice and were held out of the scrimmage.

Johnson said both Watson and Bogans are considered day-to-day, while Blatche and Childress both are expected to practice today.